Photo-conductor plate reduced in light reflection, and surface emitting device and liquid crystal display unit using it

ABSTRACT

A liquid crystal display unit equipped with a photo-conductor plate serving to enhance light transmittance by reducing a reflection of light on its emission face and reflection face and a surface emitting device provided with this photo-conductor plate to be able to achieve efficient irradiation with light, and a liquid crystal display unit providing satisfactory contrast and excelling in displaying quality is to be provided. In a liquid crystal display unit configured of a photo-conductor plate provided with a substrate having a light emission face for emitting light introduced within from a light source via a side end face and a reflection face, positioned on the other side than the light emission face for reflecting the light propagating inside, and anti-reflection films provided over a surface of the substrate, and a liquid crystal display unit arranged opposite the light emission face of the photo-conductor plate, wherein the anti-reflection films are provided over at least the light emission face and the reflection face.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a photo-conductor plate and itsmanufacturing method, a surface emitting device and a liquid crystaldisplay unit, and more particularly to the structure of aphoto-conductor plate excelling in light transmittance when used as thefront light of a liquid crystal display unit.

[0003] 2. Description of the Prior Art

[0004] Usually, in a reflex liquid crystal display unit using ambientlight as the light source for displaying, its luminance is affected bythe luminous energy of the ambient light, and therefore involves theproblem that the visibility of the display extremely deteriorates in adark place or any other environment where no sufficient ambient light isavailable.

[0005] Accordingly, in order to solve the above-noted problem, there isproposed a liquid crystal display unit of a type in which a front light(surface emitting device) is arranged on the front side of a reflexliquid crystal display unit for use as an auxiliary light source. Thisfront light-equipped liquid crystal display unit operates as a usualreflex liquid crystal display unit in an environment where sufficientambient light is available, such as outdoors in the daytime, and thefront light is turned on as required to serve as a light source. Asectional structure of an example of such a liquid crystal display unitin which a front light is arranged on the front side of a liquid crystaldisplay unit is shown in FIG. 8. This liquid crystal display unit 200shown in FIG. 8 is configured of a liquid crystal display unit 220 and afront light 210, and the front light 210 is arranged on the front face(top face in FIG. 8) of the liquid crystal display unit 220 so that aphoto-conductor plate 212 is arranged in the display area of the liquidcrystal display unit 220.

[0006] The front light 210 is configured of a photo-conductor plate 212formed by injection molding of transparent acrylic resin or the like anda light source 213 formed of a cold-cathode tube arranged on a side endface 212 a of this photo-conductor plate 212. The bottom face (the sidetoward the liquid crystal display unit 220) of the photo-conductor plate212 is used as a light emission face 212 b from which light is emitted.The other face (the top face of the photo-conductor plate 212) than thislight emission face 212 b is used as a reflection face 212 c where afirst slope 216 and a second slope 217 ensuing from it, formed at aninclination with respect to the light emission face 212 b, arealternately and periodically arranged to alter the direction of lightwithin the photo-conductor plate 212. To the light emission face 212 bof the photo-conductor plate 212 is stuck an anti-reflection film 215.

[0007] The liquid crystal display unit 220 has a configuration in whicha first substrate 221 and a second substrate 222 facing each other witha liquid crystal layer 223 pinched between them are integrated byjoining with a sealing material 224. On the side of the first substrate221 toward the liquid crystal layer 223 are successively stacked areflection layer 225, containing a reflection film for reflecting lighthaving come incident on the liquid crystal display unit 220, and adisplay circuit 226 for driving and controlling the liquid crystal layer223, and a display circuit 227 is provided on the side of the secondsubstrate 222 toward the liquid crystal layer 223.

[0008] In the liquid crystal display unit 200 configured as describedabove, light emitted from the light source 213 is introduced into thephoto-conductor plate 212 via the side end face 212 a of thephoto-conductor plate 212, propagates within photo-conductor plate 212and at the same time is reflected by the first slope 216 having agreater angle of inclination with respect to the direction of lightintroduction to undergo a change in its propagating direction toward thelight emission face 212 b, eventually to be emitted from the lightemission face 212 b. This light emitted from the light emission face 212b comes incident on the liquid crystal display unit 220 as illuminatinglight, passes the display circuits 226 and 227 and the liquid crystallayer 223, is reflected by the reflection layer 225, returns to outsidethe liquid crystal display unit 220, and is transmitted by the lightemission face 212 b and the reflection face 212 c of the photo-conductorplate 212 to reach the observer. In this way, the display on the liquidcrystal display unit 220 is recognized by the observer.

[0009] However, the front light 210 of the liquid crystal display unit200 configured as described above involves the problem that, as theanti-reflection film 215 is provided only on the light emission face 212b of the photo-conductor plate 212, contrast is reduced by reflectionfrom either the inside or the surface of the photo-conductor plate 212.This is due to the reason explained below.

[0010] First, with the front light 210 described above, the light comingincident from outside on the reflection face 212 c of the front light210 is reflected by this reflection face 212 c and directly reaches theobserver to adversely affect his or her perception of the display.

[0011] Then, the light introduced from the light source 213 into thephoto-conductor plate 212 via the side end face 212 a of thephoto-conductor plate 212 propagates within the photo-conductor plate212. At the same time, its propagating direction is turned toward thelight emission face 212 b by the first slopes 216, steeper of the slopes216 and 217 formed on the reflection face 212 c, and about 96% of thelight is emitted from the light emission face 212 b to illuminate thereflex liquid crystal display unit 220. However, about 4% of it isreflected by the light emission face 212 b to become reflected lightdirected to the reflection face 212 c, passes the reflection face 212 cand is emitted outside to reach the observer. Such reflected lightreaches the observer without passing the liquid crystal display unit220, and therefore does not contribute to displaying. Therefore, thisreflected light is perceived by the observer as noise, and contributesto the deterioration of contrast. Furthermore, as the reflected light isgenerated from the light reflected by the periodically formed firstslopes 216 and passes the reflection face 212 c on which the slopes 216and 217 are periodically formed to reach the observer, it involves therisk of allowing moiré to be generated by interference due to theperiodicity of the slopes 216 and 217.

[0012] Next, as described above, the light from the light source 213,whose propagating direction is changed by the slopes 216 formed insuccession periodically on the reflection face 212 c of thephoto-conductor plate 212, is emitted from the light emission face 212 bto illuminate the reflex liquid crystal display unit 220. The lightcoming incident on this liquid crystal display unit 220 is reflected bythe reflection layer 225 of the liquid crystal display unit 220 towardthe front light 210, and again comes incident on the photo-conductorplate 212. Part of the light traveling from this liquid crystal displayunit 220 toward the front light 210 is reflected by the light emissionface 212 b and the reflection face 212 c of the photo-conductor plate212 to generate light which does not contribute to displaying butinvites deterioration in contrast.

SUMMARY OF THE INVENTION

[0013] An object of the present invention, attempted in view of theabove-described circumstances, is to provide a liquid crystal displayunit equipped with a photo-conductor plate serving to enhance lighttransmittance by reducing reflection of light on its emission face andreflection face and a surface emitting device provided with thisphoto-conductor plate to be able to achieve efficient irradiation withlight, and a liquid crystal display unit providing satisfactory contrastand excelling in displaying quality.

[0014] The above-stated object can be achieved with a photo-conductorplate provided with a substrate having a light emission face foremitting light introduced within via a side end face and a reflectionface, positioned on the other side than the light emission face, forreflecting light propagating inside, and anti-reflection films providedover a surface of the substrate, wherein the anti-reflection films areprovided over at least the light emission face and the reflection face.

[0015] It is preferable that a reflectance of the anti-reflection filmsis 1% or less of a reflectance of an Al film at an optical wavelength of550 nm.

[0016] It is preferable that the reflectance of the anti-reflectionfilms is 2.5% or less of the Al film in an optical wavelength range of380 nm to 780 nm. It is further preferable that the reflectance of theanti-reflection films is 1.5% or less of the Al film in an opticalwavelength range of 450 nm to 700 nm.

[0017] It is preferable that a refractive index of the substrate is notless than 1.48, and a refractive index of the anti-reflection films isnot more than 1.35.

[0018] It is preferable that the anti-reflection films are formed by adip coating process.

[0019] It is preferable that the anti-reflection films are asingle-layered structure.

[0020] The above-stated object can also be achieved with a surfaceemitting device provided with a photo-conductor plate according to theinvention and a light source arranged on an incident end face of thephoto-conductor plate.

[0021] The above-stated object can as well be achieved with a liquidcrystal display unit provided with the surface emitting device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 shows a section of a liquid crystal display unit in a modeof implementing the present invention.

[0023]FIG. 2 shows an expanded perspective view of part of thereflection layer of the liquid crystal display unit according to theinvention.

[0024]FIG. 3A through FIG. 3C are configurational diagrams showing anexample of a formation method for anti-reflection films according to theinvention.

[0025]FIG. 4 is a graph showing a result of measurement of the filmthickness distribution of the anti-reflection films by atomic forcemicroscopy (AFM).

[0026]FIG. 5 illustrates an example of a method of measuring thethickness of the anti-reflection films of the photo-conductor plate.

[0027]FIG. 6 shows a result of measurement of the reflectance of theanti-reflection films of Embodiment 1 of the invention.

[0028]FIG. 7 shows a result of measurement of the contrast ratio of theliquid crystal display unit of Embodiment 2 of the invention.

[0029]FIG. 8 shows a section of a liquid crystal display unit of asurface emitting device according to the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Whereas preferred embodiments of the present invention will bedescribed below with reference to accompanying drawings, the inventionis not limited to these modes of implementation. The drawings referredto in describing these modes of implementation are mere aids todescription of the configurations of the photo-conductor plate, surfaceemitting device and liquid crystal display unit, and the lengths, widthsand thicknesses of these elements are different from those of the realphoto-conductor plate, surface emitting device and liquid crystaldisplay unit.

[0031]FIG. 1 shows a section of a liquid crystal display unit providedwith a front light (surface emitting device) in a mode of implementingthe present invention. In FIG. 1, the schematic configuration of aliquid crystal display unit 1 consists of a liquid crystal display unit20 and a front light 10 arranged in front of this liquid crystal displayunit 20 to illuminate the liquid crystal display unit 20. The frontlight 10 is composed of a transparent photo-conductor plate 12 and alight source 13, and the light source 13 is arranged on a side end face12 a for introducing light into the photo-conductor plate 12.

[0032] The photo-conductor plate 12, arranged on the front side (topface in FIG. 1) of the display area of the liquid crystal display unit20 to irradiate the liquid crystal display unit 20 with light from thelight source 13 is configured of a substrate 11 consisting oftransparent acrylic resin or the like and transparent anti-reflectionfilms 15 and 18 provided on the bottom and top faces of the substrate11. As illustrated in FIG. 1, the bottom face (the face opposite theliquid crystal display unit 20) of the photo-conductor plate 12 is alight emission face 12 b from which light to illuminate the liquidcrystal display unit 20 is emitted, and the top face (external face ofthe photo-conductor plate 12) on the other side than this light emissionface 12 b is a reflection face 12 c for altering the direction of thelight propagating within the photo-conductor plate 12.

[0033] The material to constitute the substrate 11 of thephoto-conductor plate 12 maybe selected from transparent resin materialsincluding polycarbonate resin and epoxy resin besides acrylic resin, andglass. To cite a specific example, a suitable, though not the only,choice would be ARTON (trade name of a product available from JSR).

[0034] The light emission face 12 b of the photo-conductor plate 12 is asurface which is arranged opposite the liquid crystal display unit 20and from which light for illuminating the liquid crystal display unit 20is emitted. It is a smooth surface of 10 nm or less in roughness (Ra).The anti-reflection film 15 is provided over this light emission face 12b to prevent light reflection.

[0035] In the reflection face 12 c are formed a plurality ofwedge-shaped grooves 14 in stripes, each consisting of a first slope 16and a second slope 17 following this first slope 16, inclined withrespect to the light emission face 12 b to reflect the light propagatingwithin the photo-conductor plate 12 and change its propagatingdirection. Out of the first slopes 16 and the second slopes 17constituting the grooves 14, the first slopes 16 have a steeper angle ofinclination. Also, the anti-reflection film 18 is provided over thisreflection face 12 c to prevent light reflection.

[0036] Although the reflection face 12 c of the photo-conductor plate 12shown in FIG. 1 is formed in a triangle wave shape consisting of aseries of wedge-shaped grooves 14, it may as well consist of a series oftrapezoids having a flat part substantially parallel to the lightemission face 12 b between each adjoining pair of grooves 14, aplurality of concaves constituting part of a spherical surface, or aplurality of convexes constituting part of a spherical surface formed onthe reflection face 12 c.

[0037] As the light source 13, a cold-cathode tube, an organic ELelement, an LED, a combination of an LED and a rod-shapedphoto-conductor or anything else that can uniformly irradiate the sideend face 12 a of the photo-conductor plate 12 with light can be suitablyused.

[0038] The liquid crystal display unit 20 is composed by integrallyjoining with a sealing material 24 a first substrate 21 and a secondsubstrate 22, both consisting of glass or the like, opposite to eachother pinching a liquid crystal layer 23 between them. Over the face ofthe first substrate 21 toward the liquid crystal layer 23 are stacked areflection layer 25 containing a metallic reflection film and a displaycircuit 26 in that order, and over the face of the second substrate 22toward the liquid crystal layer 23 is formed a display circuit 27. Thusthe liquid crystal display unit 20 is a reflex liquid crystal displayunit provided with the reflection layer 25 for reflecting light comingincident from outside.

[0039] The display circuits 26 and 27, though not shown, includeelectrode layers, consisting of transparent electroconductive films orthe like, for driving the liquid crystal layer 23, and alignment layersor the like for controlling the alignment of the liquid crystal layer23. In some cases, they may have color filters for color displaying.

[0040] The reflection layer 25 is configured, for instance, bysputtering a metallic reflection film consisting of aluminum, silver orthe like over an organic film consisting of acrylic resin or the likehaving a rugged surface, and forming a flattening film consisting ofsilicone resin or the like to cover these reflection film and organicfilm. This reflection layer 25 may include a color filter, which, if itis to be included, should preferably be formed immediately above thereflection film. Since this configuration would allow the color filterto be arranged on the light reflection face, high grade color displayingwould be made possible with reduced color shifts and parallax.

[0041] Now will be described with reference to FIG. 2 the shapes of thesurface of the organic film formed over the reflection layer 25 of theliquid crystal display unit 20 and of the reflection film formed overthe organic film.

[0042]FIG. 2 shows an expanded perspective view of part of the organicfilm and the reflection film formed over the reflection layer 25 of theliquid crystal display unit 20. As illustrated in this drawing, manyconcaves 28 a each of which has an inner face constituting part of asphere are formed on the surface of the organic film 28 overlapping oneanother, and over this organic film 28 is formed the reflection film 29.

[0043] The organic film 28 is formed by, after forming in a flat shape aresin layer consisting of photosensitive resin or the like over thesubstrate, pressure-fitting a transfer mold consisting of acrylic resinor the like and having an inversely rugged surface shape to the organicfilm 28 shown in FIG. 2, and then hardening the resin layer. Thereflection film 29, formed over the surface of the organic film 28, isintended to reflect light coming incident on the liquid crystal displayunit 20. It is formed by sputtering, vacuum vapor-depositing orsubjecting to some other film formation process a metallic materialhaving a high reflectance, such as aluminum or silver.

[0044] It is preferable for the concaves 28 a shown in FIG. 2 to beformed in random depths within the range of 0.1 μm to 3 μm, for thepitch of spacing between adjoining concaves 28 a to be set at randomwithin the range of 5 μm to 100 μm, and for the inclination of the innerfaces of the concaves 28 a to be set between −30 degrees and +30degrees.

[0045] Points of particular importance are that the inclination of theinner faces of the concaves 28 a is set between −30 degrees and +30degrees and that the pitch of spacing between adjoining concaves 28 a isset at random in all directions over the plane, because any regularityof the pitch of spacing between adjoining concaves 28 a would give riseto interference colors of light to color the reflected light. Or if theinclination of the inner faces of the concaves 28 a is out of the rangeof −30 degrees to +30 degrees, the diffusion angle of the reflectedlight will become too wide, and no bright display can be achieved(because the diffusion angle of the reflected light reaches or surpasses36 degrees in the air, and the reflection intensity peak within theliquid crystal display unit drops, resulting in a large total reflectionloss).

[0046] Or if the depth of the concaves 28 a is greater than 3 μm, thepeaks of the convexes cannot be fully covered by the flattening filmwhen the concaves 28 a are to be flattened at a later step, and thedesired degree of flatness cannot be achieved.

[0047] Where the pitch of spacing between adjoining concaves 28 a isless than 5 μm, there is a constraint on the fabrication of the transfermold for use in forming the organic film 28, entailing the problems ofan extremely long time taken for processing, impossibility to form anadequate shape for achieving the desired reflection characteristics andthe generation of interference lights. Whereas the transfer mold for usein forming the surface shape of the organic film 28 is fabricated bytransferring the surface shape of the matrix for the transfer moldproduced by pressing many diamond indenters on a substrate of stainlesssteel or the like to silicone resin or the like, it is preferable forthe tips of these diamond indenters to be between 30 μm and 200 μm indiameter for practical usefulness, and accordingly it is preferable forthe pitch of spacing between adjoining concaves 28 a to be between 5 μmand 100 μm.

[0048] The liquid crystal display unit 20 can efficiently reflect andscatter light coming incident from outside because the reflection film29 constituting the reflection layer 25 is shaped as described above,resulting in bright reflex displaying and a wide angle of field ofvision. This is due to the facts that the depth and pitch of theconcaves 28 a shown in FIG. 2 are controlled within the respectiveranges described above and that the inner faces of the concaves 28 a arespherical.

[0049] Thus, as the formation of the concaves 28 a in the controlleddepth and pitch serves to keep the inclination angle of the inner facesof the concaves 28 a, which govern the reflection angle of light, it ismade possible to control the reflection efficiency of the reflectionfilm 29 within a certain range. Also, because the inner faces of theconcaves 28 a are spheres which are symmetric in all directions, thereflection efficiency can be obtained in every direction of thereflection film 29. Thus, the display can be bright irrespective of thedirection in which the observer sees it.

[0050] The liquid crystal display unit 1 configured as described abovecan use the front light 10, when it is turned on, for reflex displayingbesides using ambient light, such as sunlight or artificialillumination, for reflex displaying.

[0051] Light introduced from the light source 13 of the front light 10into the photo-conductor plate 12 via the side end face 12 a of thephoto-conductor plate 12 not only propagates within the photo-conductorplate 12 but also, reflected by the first slope 16 s constituting thegrooves 14 which are formed on the reflection face 12 c of thephoto-conductor plate 12, is changed in propagating direction toward thelight emission face 12 b, and emitted from the light emission face 12 bof the photo-conductor plate 12 to illuminate the liquid crystal displayunit 20. Light coming incident on the liquid crystal display unit 20passes the display circuits 26 and 27 and the liquid crystal layer 23 ofthe liquid crystal display unit 20, reaches the reflection layer 25, isreflected by the reflection film of this reflection layer 25, returns tooutside the liquid crystal display unit 20, passes the photo-conductorplate 12 to be emitted from the reflection face 12 c, and reaches theobserver. In this way, the display on the liquid crystal display unit 20is perceived by the observer.

[0052] It is preferable for the reflectance for light coming incident atan angle of not greater than 5 degrees on the light emission face 12 bprovided with the anti-reflection film 15 to be not more than 1% of thelight reflectance of the Al film, because if the light reflectance at awavelength of 550 nm surpasses 1%, reflected light generated on thelight emission face 12 b of the photo-conductor plate 12 and thereflection face 12 c will reduce the contrast of the liquid crystaldisplay unit 1.

[0053] It is further preferable for the reflectance of theanti-reflection films not to be more than 2.5% of the reflectance of theAl film in the region of 380 nm to 780 nm in optical wavelength, becauseif the reflectance of the anti-reflection films surpasses 2.5%, thefluctuations of reflectance in the visible light region will increase,with the result that much of light of a specific wavelength is reflectedand the photo-conductor plate 12 is perceivably colored.

[0054] Also it is preferable for the reflectance of the anti-reflectionfilms to be not more than 1.5% in the optical wavelength region of 450nm to 700 nm, because such a configuration would enable the liquidcrystal display unit 1 to give a white display of high luminance andcolor purity.

[0055] The light emission face 12 b and the reflection face 12 c of thephoto-conductor plate 12 are provided with the anti-reflection films 15and 18 for preventing the reflection of light coming incident on thesefaces from inside and outside the photo-conductor plate, and theseanti-reflection films 15 and 18 enable the liquid crystal display unit 1in this mode of implementing the invention to provide satisfactoryperceptibility.

[0056] First will be described a case in which reflex displaying is doneby the liquid crystal display unit 1 shown in FIG. 1 using ambientlight. As the anti-reflection film 18 is provided on the reflection face12 c of the photo-conductor plate 12, which constitutes the outermostface of the liquid crystal display unit 1 shown in FIG. 1, thereflectance of external light coming incident on this reflection face 12c can be kept low as described above. Thus, it is possible to preventthe perceptibility of the display on the liquid crystal display unit 1from being significantly deteriorated by strong reflection of light in aspecific direction by the reflection face 12 c.

[0057] Light coming incident on the photo-conductor plate 12 fromoutside via the reflection face 12 c passes the light emission face 12 bto be incident on the liquid crystal display unit 20. As this lightemission face 12 b is also provided with the anti-reflection film 15,light reflected by the light emission face 12 b can be kept at not morethan 1% of light having a wavelength of 550 nm as stated above.Therefore, the light that is reflected by the light emission face 12 bto return outside to deteriorate the perceptibility of the display onthe liquid crystal display unit 1 can be reduced.

[0058] Since the liquid crystal display unit 1 according to theinvention is provided with the front light 10 having the photo-conductorplate 12 which, by providing each face which is to transmit light withan anti-reflection film, can reduce the light reflected by each face, itcan efficiently utilize ambient light to achieve reflex displaying ofsatisfactory perceptibility.

[0059] Next will be described a case in which the front light 10 isturned on to perform displaying. In this case, light from the lightsource 13 propagating within the photo-conductor plate 12 shown in FIG.1 is reflected by the slopes 16 to be altered in propagating directionand passes the light emission face 12 b to come incident on the liquidcrystal display unit 20. This light emission face 12 b is provided withthe anti-reflection film 15. Therefore, out of the quantity of lightcoming incident on the light emission face 12 b, the part that isreflected by the light emission face 12 b, passes the reflection face 12c and is emitted out to reach the observer can be reduced compared withthe prior art.

[0060] Then, the light coming incident on the liquid crystal displayunit 20 is reflected by the reflection layer 25 to come incident on thephoto-conductor plate 12 again via the light emission face 12 b. As thereflectance of this light passing the light emission face 12 b is alsokept at 1% or below by the anti-reflection film 15, the quantity oflight reflected by the light emission face 12 b to return to the liquidcrystal display unit 20 can be reduced. Therefore, it is made possibleto prevent such light as does not contribute to displaying from comingincident on the liquid crystal display unit 20 and inviting whitedimming or any other trouble.

[0061] Next, whereas the light coming incident on the photo-conductorplate 12 from the liquid crystal display unit 20 side via the lightemission face 12 b passes the reflection face 12 c to reach theobserver, this light, when passing the reflection face 12 c, is alsoreflected by the reflection face 12 c to generate light that returns toinside the photo-conductor plate 12. Since this returning light, too,can be reduced by the anti-reflection film 18 provided on the reflectionface 12 c, it is made possible to prevent light making no contributionto displaying from remaining within the front light 10 or the liquidcrystal display unit 20 and adversely affecting perceptibility.

[0062] Thus, the liquid crystal display unit 1 according to theinvention can provide high grade displaying excelling in perceptibilitywhether reflex displaying uses ambient light or uses the front light 10that is turned on for the purpose.

[0063] The anti-reflection films 15 and 18 of the photo-conductor plate12 can be formed by dip coating. One example of anti-reflection filmformation by dip coating will be described with reference to FIGS. 3.FIGS. 3 are process diagrams illustrating one example of formationmethod for anti-reflection films according to the invention, whereinFIGS. 3A through 3C show steps of the process in that order.

[0064] First, as shown in FIG. 3A, side end faces 30 a and 30 b of asubstrate 30 fabricated by injection molding of a resin material, suchas transparent acrylic resin or polycarbonate resin, are respectivelyprovided with masks 31 a and 31 b, composed of triacetate or the like,to prevent an anti-reflection film from being formed on the side endface 30 a. A plurality of wedge-shaped grooves 32 are formed in one faceof the substrate 30 in stripes, and the other face than that in whichthe grooves 32 are formed, though not shown, is flat. The side end face30 a is also flat.

[0065] Then, as shown in FIG. 3B, while supporting one end of thissubstrate 30, the substrate 30 is placed in a vessel 34 filled with aresin solution 33 for forming anti-reflection films. Next, thissubstrate 30 is held for 1 to 5 minutes in a state of being whollyimmersed in the resin solution 33. For this resin solution 33, asuitable, though not the only, choice may be CYTOP (trade name of aproduct available from ASAHI GLASS).

[0066] Then, as shown in FIG. 3C, the substrate 30 is lifted toward theupper part of the vessel 34 at a rate of 150 mm/min to 300 mm/min. It ispreferable for this lifting to be accomplished while supporting thesubstrate 30 in such a manner that the lengthwise direction of thewedge-shaped grooves 32 formed in strips in one face of the substrate 30is parallel to the lifting direction. If lifting is done in a directionorthogonal to the lengthwise direction of the grooves 32, the resinsolution 33 will accumulate on the convexes between adjoining grooves 32to make uneven the thickness of the anti-reflection film that is formed.

[0067]FIG. 4 illustrates the result of measurement of theanti-reflection film thickness by atomic force microscopy (AFM) ofphoto-conductor plates over anti-reflection films were actually formedby lifting in different lifting directions. The AFM measurement wasperformed by scanning with an AFM probe 36 the vicinities of the peaksof convexes 35, whose section is partially shown in FIG. 5, formedbetween adjoining grooves 32 in the substrate 30.

[0068] The solid curve in FIG. 4 represents the shape of the convexes 35of the substrate 30 where no anti-reflection film is formed. The one-dotchain curve in FIG. 4 represents the result of measurement of ananti-reflection film formed by lifting the substrate 30 from the resinsolution 33 in a direction parallel to the lengthwise direction of thegrooves 32, while the two-dot chain curve represents the result ofmeasurement of an anti-reflection film formed by lifting the substrate30 in a direction orthogonal to the lengthwise direction of the grooves32. Therefore, the differences of these one-dot and two-dot chain curvesfrom the solid curve indicate the thicknesses of the anti-reflectionfilms formed on the substrate 30.

[0069] As illustrated here, compared with the anti-reflection filmformed by lifting in the direction parallel to the lengthwise directionof the grooves 32 (the two-dot chain curve), the anti-reflection filmformed by lifting in the direction orthogonal to the lengthwisedirection of the grooves 32 (one-dot chain curve) has a greater overallthickness, and is especially thick in the parts of the slope close tothe peaks of the convexes 35, therefore inferior in evenness.

[0070] Next, the substrate 30 coated with the resin solution 33 at theforegoing step is dried by putting it into an oven heated to between 70°C. to 90° C. This results in drying and solidification of the resinsolution 33 covering the substrate 30 to form an anti-reflection film.Then, the masks 3 a and 3 b are removed to provide a photo-conductorplate in which an anti-reflection film is formed on every face of thesubstrate 30 except the side end face 30 a.

[0071] The above-described production method enables an extremely thinanti-reflection film, 0.1 μm or so, to be uniformly over an uneven face,such as the face of the substrate 30 in which the wedge-shaped grooves32 are formed as shown in FIG. 3A. Therefore, as this method makes itpossible to provide a plurality of faces of the substrate withanti-reflection films, a photo-conductor plate excelling in lighttransmittance can be fabricated. Moreover, as the anti-reflection filmscan be formed simultaneously over a plurality of faces, themanufacturing process can be simplified, with corresponding reduction inthe manufacturing cost of photo-conductor plates.

[0072] The above-described production method also allows anti-reflectionfilms to be structured in a single layer, because the lighttransmittance of the anti-reflection films according to the invention isequal to, or even higher than, that of a multi-layered anti-reflectionfilm according to the prior art. Thus, as the anti-reflection filmformed by dip coating is extremely thin and uniform, it can exertparticularly high light transmittance. However, it is of coursepermissible to use a multi-layered structure in some cases, and in suchcases the structure can be formed by uniformly stacking very thinlayers.

[0073] Further, by configuring a front light using a photo-conductorplate fabricated by the above-described production method and arrangingit on the front side of a liquid crystal display unit, the excellentlight transmittance of the photo-conductor plate can provide a liquidcrystal display unit with satisfactory perceptibility of display,because the displaying by the liquid crystal display unit transmitted bythe photo-conductor plate is satisfactory and the front light canefficiently illuminate the liquid crystal display unit.

Preferred Embodiments Embodiment 1

[0074] First, by performing injection molding with ARTON (trade name ofa product available from JSR) as the material, a substrate in which aplurality of wedge-shaped grooves were formed in stripes all over wasfabricated. The face in which the wedge-shaped grooves are formed is thereflection face of this substrate, and the other face is the lightemission face. The refractive index of this substrate was 1.52.

[0075] Next, masks were arranged on the side end faces of thephoto-conductor plate to cover these faces and, after soaking thissubstrate in CYTOP (trade name of a product available from ASAHI GLASS),it was lifted at a rate of 210 mm/min and coated with the aforementionedsolution. Then, this substrate was dried for one hour in an oven heatedto 90° C. to fabricate a photo-conductor plate by forminganti-reflection films of 0.1 μm in thickness over the surface of thesubstrate. The refractive index of these anti-reflection films of thephoto-conductor plate was 1.34.

[0076] Then, after removing the masks on the side end faces of thephoto-conductor plate, a light source equipped with a white LED wasarranged on a side end face of the photo-conductor plate to configure afront light, and a liquid crystal display unit was produced by arrangingthis front light on the front side of the reflex liquid crystal displayunit.

[0077] In a state in which the front light of the liquid crystal displayunit is not turned on, the reflectance at the time when reflected lightfrom the liquid crystal display unit passes the photo-conductor platewhere the angle of incident on the liquid crystal display unit was 30degrees and the angle of observation was 0 degree was measured withLCD-7000 (trade name of a product available from OTSUKA ELECTRONICS).The reflectance ratio between black displaying and white displaying ofthe liquid crystal display unit was calculated on the basis of theresult of measurement to be used as the contrast ratio. The contrastratio of the liquid crystal display unit of this embodiment based onthis measurement was 13.

[0078] Next, the light emission face of the photo-conductor plate wasirradiated with light, and its reflectance was measured with aspectroscope. The result is shown in FIG. 6, in which the horizontalaxis represents the optical wavelength and the vertical axis, thereflectance of light of the corresponding wavelength on the horizontalaxis. It is to be noted that the reflectance on the vertical axis isexpressed in % of the reflectance of an Al film. As shown in FIG. 6, thereflectance of the anti-reflection films of the photo-conductor plateembodying the invention in this manner was 1% or less of the reflectanceof the Al film at an optical wavelength of 550 nm, and 2.5% or less ofthe reflectance of the Al film in a wavelength region of 380 nm to 780nm. It was 1% or less of the reflectance of the Al film in a wavelengthregion of 500 nm to 700 nm, and 1.5% or less of the reflectance of theAl film in a wavelength region of 450 nm to 700 nm.

Embodiment 2

[0079] Next, at the step for forming anti-reflection films over asubstrate fabricated by the same method as that for Embodiment 1,photo-conductor plates were produced, each by forming theanti-reflection films so that its reflectance at an optical wavelengthof 550 nm be 0.6%, 0.9%, 1.45%, 2.3% or 4.3% of the Al film by varyingthe combination of the material and thickness of the film in a vapordeposition process. A photo-conductor plate whose reflectance is 4.3%out of the reflectance ratios mentioned above has no anti-reflectionfilms formed over it. Then, using these photo-conductor plates, liquidcrystal display units were fabricated in the same manner as forEmbodiment 1.

[0080] The result of measurement of the contrast ratios of these liquidcrystal display units with BM5 (trade name of a product available fromTOPCON) is shown in FIG. 7, wherein the horizontal axis represents thereflectance of the anti-reflection films and the vertical axis, thecontrast ratios of the liquid crystal display units provided with therespective photo-conductor plates. Each of these contrast ratios refersto the luminance level of the liquid crystal display unit in the normaldirection in black displaying and white displaying by the liquid crystaldisplay unit measured in a state in which the front light is on.

[0081] As illustrated in FIG. 7, if the reflectance of theanti-reflection films at an optical wavelength of 550 nm is not morethan 1%, the contrast ratio of the liquid crystal display unit will showa high level of or above 7.7, but if the reflectance surpasses 1%, thecontrast ratio will gradually drop, down to 5 at a reflectance of 4.3%.Thus, if the reflectance of the anti-reflection films is not more than1% of that of the Al film, it will be possible to increase the contrastratio of the liquid crystal display unit by preventing the white dimmingof the display which would result from light generated by the reflectionon the light emission face when reflected light from the liquid crystaldisplay unit passes the photo-conductor plate and reaches the observer.

Comparative Example 1

[0082] Next, as Comparative Example 1, a liquid crystal display unit wasproduced, in the same way as for Embodiment 1 except that ananti-reflection film was formed only on the light emission face, byarranging masks on side end faces and reflection faces of a substratefabricated by injection molding and then forming an anti-reflectionfilm.

[0083] The front light of this liquid crystal display unit was turned onand displaying was performed. The contrast measured in the same manneras for Embodiment 1 was found to be 8.

Comparative Example 2

[0084] Then, as Comparative Example 2, a photo-conductor plate usingcommercially available anti-reflection films was produced. First, asubstrate in which wedge-shaped grooves were formed in stripes all overwas fabricated by an injection molding process using Delpet (trade nameof a product available from Asahi Kasei), which is an acrylic resin. Theface in which the wedge-shaped grooves are formed is the reflection faceof this substrate, and the other face is the light emission face. Therefractive index of this substrate was 1.49.

[0085] Next, a photo-conductor plate was produced by sticking ananti-reflection film to the light emission face of the substrate. Theanti-reflection film that was used was a commercially available onehaving a refractive index of 1.38.

[0086] Then, a light source equipped with a white LED was arranged on aside end face of the photo-conductor plate to configure a front light,and a liquid crystal display unit was produced by arranging this frontlight on the front side of the reflex liquid crystal display unit.

[0087] The front light of this liquid crystal display unit was turned onand displaying was performed. The contrast measured in the same manneras for Embodiment 1 was found to be 8.

[0088] The results obtained with these Embodiment 1, Comparative Example1 and Comparative Example 2 have revealed that a liquid crystal displayunit equipped with a front light using a photo-conductor plate providedwith anti-reflection films both on the emission and reflection facesaccording to the invention excels in contrast.

[0089] As hitherto described in detail, the photo-conductor plateaccording to the present invention is provided with a substrate having alight emission face for emitting light introduced within via a side endface and a reflection face, positioned on the other side than the lightemission face, for reflecting light propagating inside, andanti-reflection films provided over surfaces of the substrate, whereinthe anti-reflection films are provided over at least the light emissionface and the reflection face. Accordingly, it can exert excellent lighttransmittance by restraining the reflection of light coming incident onthe light emission face and the reflection from inside or outside thephoto-conductor plate.

[0090] Further, by keeping the reflectance of the anti-reflection filmsof the photo-conductor plate according to the invention at 1% or less ofthe reflectance of an Al film at an optical wavelength of 550 nm, aphoto-conductor plate excelling in light transmittance can be provided,and accordingly the contrast ratio of displaying can be prevented fromdeteriorating in a liquid crystal display unit wherein thephoto-conductor plate is arranged on the front side to performdisplaying with transmission by the photo-conductor plate.

[0091] Or, by keeping the reflectance of the anti-reflection films at2.5% or less of the reflectance of the Al film in an optical wave lengthregion of 380 nm to 780 nm, it is made possible to prevent thephenomenon in which light of a specific wavelength is significantlyreflected and the photo-conductor plate 12 is perceivably colored.

[0092] Or, by keeping the reflectance of the anti-reflection films at1.5% or less of the reflectance of the Al film in an optical wave lengthregion of 450 nm to 700 nm, it is made possible to keep the intensitiesof lights passing the photo-conductor plate in a broad wavelengthregion, and accordingly displaying at high luminance and color purity ismade possible.

[0093] Next, by keeping the refractive index of the substrate of thephoto-conductor plate according to the invention at 1.48 or more and therefractive index of the anti-reflection films at 1.35 or less, lightpropagating within the photo-conductor plate can be confined within thephoto-conductor plate, and accordingly the propagation loss of light canbe suppressed to enhance the efficiency of the light source.

[0094] Then, by structuring the anti-reflection films of thephoto-conductor plate according to the invention in a single layer, thestructure of the anti-reflection films can be simplified with acorresponding reduction in manufacturing cost.

[0095] Particularly if the anti-reflection films of the photo-conductorplate according to the invention are formed by dip coating,anti-reflection films can also be formed on the reflection face of thephoto-conductor plate where grooves and other rugged elements areformed, so that the light transmittance of the photo-conductor plate canbe enhanced tremendously.

[0096] Next, a photo-conductor plate production method according to theinvention comprises a step of soaking a flat substrate on one of whosefaces are formed wedge-shaped grooves in stripes in a resin solutioncontaining a resin material to constitute an anti-reflection film andlifting the substrate from the resin solution thereby to coat thesubstrate with the resin solution, and a step of drying the substrate toform an anti-reflection film on its surface, wherein the direction inwhich the substrate is lifted from the resin solution is parallel to thegrooves in the substrate, and accordingly the anti-reflection film canbe formed uniformly even over the face in which the grooves are formed.Moreover, as the anti-reflection films can be formed simultaneously overa plurality of faces, the manufacturing process can be simplified, witha corresponding reduction in manufacturing cost.

[0097] Next, as a surface emitting device according to the invention isprovided with a photo-conductor plate according to the invention and alight source arranged on one side end face of the photo-conductor plate,highly efficient illumination is made possible by virtue of the highlight transmittance of the photo-conductor plate.

[0098] Also, a liquid crystal display unit according to the invention isprovided with a surface emitting device according to the invention,light from the light source of the surface emitting device can beefficiently used for illuminating the liquid crystal display unit, andat the same time the high light transmittance of the photo-conductorplate can prevent the contrast ratio of displaying from deterioratingwherein displaying is to be performed with transmission by the surfaceemitting device.

What is claimed is:
 1. A photo-conductor plate provided with a substratehaving a light emission face for emitting light introduced within via aside end face and a reflection face, positioned on the other side thanthe light emission face, for reflecting the light propagating inside,and anti-reflection films provided over a surface of the substrate,wherein the anti-reflection films are provided over at least the lightemission face and reflection face.
 2. The photo-conductor plate,according to claim 1, wherein the reflection face is provided with aplurality of slopes for reflecting the light propagating within thesubstrate to alter a propagating direction of the light.
 3. Thephoto-conductor plate, according to claim 1, wherein a reflectance ofthe anti-reflection films is 1% or less of a reflectance of an Al filmat an optical wavelength of 550 nm.
 4. The photo-conductor plate,according to claim 3, wherein the reflectance of the anti-reflectionfilms is 2.5% or less of the reflectance of the Al film in an opticalwavelength region of 380 nm to 780 nm.
 5. The photo-conductor plate,according to claim 4, wherein the reflectance of the anti-reflectionfilms is 1.5% or less of the reflectance of the Al film in an opticalwavelength region of 450 nm to 700 nm.
 6. The photo-conductor plate,according to claim 1, wherein a refractive index of the substrate is notless than 1.48 and a refractive index of the anti-reflection films isnot more than 1.35.
 7. The photo-conductor plate, according to claim 1,wherein the anti-reflection films are formed by a dip coating method. 8.The photo-conductor plate, according to claim 7, wherein theanti-reflection films are a single-layered structure.
 9. Aphoto-conductor plate production method comprising a step of soaking aflat substrate on one of whose faces are formed wedge-shaped grooves instripes in a resin solution containing a resin material to constitute ananti-reflection film and lifting the substrate from the resin solutionthereby to coat the substrate with the resin solution, and a step ofdrying the substrate to form an anti-reflection film on its surface,wherein a direction in which the substrate is lifted from the resinsolution is parallel to a lengthwise direction of the grooves in thesubstrate.
 10. A surface emitting device provided with a photo-conductorplate claimed in claim 1 and a light source arranged on an incident endface of the photo-conductor plate.
 11. The surface emitting device, asclaimed claim 10, wherein, in the photo-conductor plate, the reflectionface is provided with a plurality of slopes for reflecting the lightpropagating within the substrate to alter a propagating direction of thelight.
 12. The surface emitting device, according to claim 10, wherein,in the photo-conductor plate, a reflectance of the anti-reflection filmsis 1% or less of a reflectance of the Al film at an optical wavelengthof 550 nm.
 13. The surface emitting device, according to claim 12,wherein, in the photo-conductor plate, the reflectance of theanti-reflection films is 2.5% or less of the reflectance of the Al filmin an optical wavelength region of 380 nm to 780 nm.
 14. The surfaceemitting device, according to claim 14, wherein, in the photo-conductorplate, the reflectance of the anti-reflection films is 1.5% or less ofthe reflectance of the Al film in an optical wavelength region of 450 nmto 700 nm.
 15. The surface emitting device, according to claim 10,wherein, in the photo-conductor plate, a refractive index of thesubstrate is not less than 1.48 and a refractive index of theanti-reflection films is not more than 1.35.
 16. The surface emittingdevice, according to claim 10, wherein, in the photo-conductor plate,the anti-reflection films are formed by a dip coating method.
 17. Thesurface emitting device, according to claim 16, wherein, in thephoto-conductor plate, the anti-reflection films are a single-layeredstructure.
 18. A liquid crystal display unit provided with a surfaceemitting device claimed in claim 1.